Fix canonicalization of --url_mapping URIs in gen_snapshot

runtime/bin/dartutils.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/dartutils.h"
 
 #include "bin/crypto.h"
 #include "bin/directory.h"
 #include "bin/extensions.h"
 #include "bin/file.h"
@@ skipping 316 matching lines @@
 
 Dart_Handle DartUtils::SetWorkingDirectory() {
   IsolateData* isolate_data =
       reinterpret_cast<IsolateData*>(Dart_CurrentIsolateData());
   Dart_Handle builtin_lib = isolate_data->builtin_lib();
   Dart_Handle directory = NewString(original_working_directory);
   return SingleArgDart_Invoke(builtin_lib, "_setWorkingDirectory", directory);
 }
 
 
+Dart_Handle DartUtils::ResolveUri(Dart_Handle library_url, Dart_Handle url) {
+  const int kNumArgs = 2;
+  Dart_Handle dart_args[kNumArgs];
+  dart_args[0] = library_url;
+  dart_args[1] = url;
+  return Dart_Invoke(DartUtils::BuiltinLib(),
+                     NewString("_resolveUri"),
+                     kNumArgs,
+                     dart_args);
+}
+
+
 Dart_Handle DartUtils::ResolveUriInWorkingDirectory(Dart_Handle script_uri) {
   const int kNumArgs = 1;
   Dart_Handle dart_args[kNumArgs];
   dart_args[0] = script_uri;
   return Dart_Invoke(DartUtils::BuiltinLib(),
                      NewString("_resolveInWorkingDirectory"),
                      kNumArgs,
                      dart_args);
 }
 
@@ skipping 900 matching lines @@
       new CObjectString(CObject::NewString(os_error->message()));
   CObjectArray* result = new CObjectArray(CObject::NewArray(3));
   result->SetAt(0, new CObjectInt32(CObject::NewInt32(kOSError)));
   result->SetAt(1, new CObjectInt32(CObject::NewInt32(os_error->code())));
   result->SetAt(2, error_message);
   return result;
 }
 
 }  // namespace bin
 }  // namespace dart